Centauri Dreams
Imagining and Planning Interstellar Exploration
Propulsion Options for the Solar Gravitational Lens Mission
A mission to the Sun’s gravity focus – or more precisely, the focal ‘line’ we might begin to use at around 650 AU – is never far from my mind. Any interstellar mission we might launch within the next thirty years or so (think Breakthrough Starshot, about which more next week) will essentially be shooting blind. We have little idea what to expect at Proxima Centauri b, if that is our (logical) target. But a mission to the solar gravity focus (SGL) would give us a chance to examine any prospective target at close hand.
Indeed, so powerful are the effects if we can exploit this opportunity that we should be able to see continents, weather patterns, oceans and more if we can disentangle the Einstein Ring that the planet’s image forms as shaped by general relativity. We’ve discussed the phenomenon many a time: The Sun’s gravitational well so shapes the image of what is directly behind it as seen from the SGL so as to produce stupendous magnification, the image served up as a ‘ring’ around the Sun in the same way that astronomers now see some distant galaxies as rings around closer galaxies.
Image:The Einstein Ring and how we could sample it. By looking at different slices of the Einstein ring, enough information could be acquired for a computer deconvolution to reconstruct the planet. Credit: Geoffrey Landis (NASA GRC).
Within that ring there is bountiful information. Not only would we have an image we could reconstruct, but we also would have multipixel spectroscopy, allowing us to identify elements through the signature of light from the planet aand to map these properties in more than one dimension. So fecund is the information in the Einstein ring that we could detect all this with a spacecraft telescope no more than a meter or so in diameter. And because the SGL focal line extends to infinity, we can keep taking observations as we move outward from 650 AU to perhaps 900 AU.
Now comes JPL scientist Slava Turyshev with a trade study – an analysis made to evaluate and select the best propulsion technique to make a flight to the SGL possible within a rational timeframe, here seen as roughly thirty years. That seems like a lot, but bear in mind that even our far-flung Voyagers have yet to reach a distance that’s even halfway to the SGL region. Remember, too, that once we find a way to propel a craft to the SGL, we have to choose a trajectory so precise that our target will be exactly opposite the Sun from the spacecraft. In this business, alignment is everything.
Each new Turyshev paper into SGL territory reminds us that this work has been taken into Phase III status at the Jet Propulsion Laboratory, funded by NASA’s Institute for Advanced Concepts. The potential showstoppers of an SGL mission are daunting, and have been examined in papers that examine everything from sail design and ‘sundiver’ trajectories to deconvolution of an SGL image. Perhaps most futuristic has been the Turyshev team’s discussion of self-assembly of a payload divided into small packages into the completed observational equipment enroute. Previous Centauri Dreams articles such as Solar Gravitational Lens: Sailcraft and Inflight Assembly or Good News for a Gravitational Focus Mission may be helpful, though the pace of stories on the SGL has been accelerating, and for the complete sequence I suggest a search in the archives.
All this is bringing me around to the scope of the propulsion problem. In addition to the need for precise positioning within the SGL focal line, the spacecraft must be able to move laterally within the image, which is of considerable size. One recent calculation found that an Earth-sized planet orbiting Epsilon Eridani (10 light years away) would project an image 12.5 kilometers in diameter at 630 AU from the Sun. One envisions multiple spacecraft taking pixel samples at various locations within the image plane. The image must then be produced by integrating these samples. This is ‘deconvolution,’ turning the Einstein ring into a coherent image free of ‘noise.’
As Geoffrey Landis, who made this calculation, points out: The image is far larger than the spacecraft we send. Landis (NASA GRC) also notes that a one-meter telescope at the SGL collects the same amount of light as a telescope of 80 meters without the gravitational lens. So we definitely want to do this, but to make it happen, the spacecraft will need propulsion and power. All this has a bearing on payload, for in an environment where solar panels are not an option, we need a radioisotope or fission power source.
Back to the Turyshev paper. Propulsion emerges as perhaps the mission’s most significant challenge, although one that the author thinks can be met. Here we run into what I call the ‘generation clock,’ which is the desire to keep mission outcomes within the lifetime of researchers who launched the project. Twenty to thirty years in cruise is often mentioned in connection with the SGL mission, meaning we need the ability to reach 650 AU with our spacecraft within that timeframe. A daunting task, for it involves reaching 154 kilometers per second. On outbound trajectories we’ve yet to exceed Voyager’s 17.1 km/sec, highlighting the magnitude of the problem.
Image: JPL’s Slava Turyshev.
We can’t solve it with chemical rockets, not even with gravity assist strategies, but solar sails coupled with an Oberth maneuver loom large as a potential solution. Advances in materials science and the success of missions like the Parker Solar Probe remind us of the potential here, offering the option of deploying a sail in a tight perihelion pass to achieve a massive boost. To manage 650 AU in 20 years means we will need 32.5 AU per year. But if we can work with a perihelion pass at 0.05 AU (7,500,000 km), we can achieve that speed, and the Parker probe has already proven we know how to do this. Finding the metamaterials to make a sail survive such a passage is an ongoing task.
The paper sums the issue up:
Recent “extreme solar sailing” studies emphasize that very fast transits are achievable in principle only by combining ultra-low total areal density with very deep perihelia (a few solar radii), which moves the feasibility question from trajectory mechanics to coupled materials, thermal, and large-area deployment qualification. For example, [Davoyan et al., 2021] analyzed extreme-proximity solar sailing (≲ 5 R⊙) and discussed candidate metamaterial sail approaches together with the associated environmental and system challenges at these perihelia. These results reinforce the conclusion here: sub-20 yr sail-only access is not ruled out by physics, but it lives in a tightly coupled materials+structures+thermal qualification regime at mission scale.
So we have a lot to learn to make this happen. The paper notes that as we move from current sail readiness to what we will need for the SGL mission, we go from sails that are in the 10-meter class up to sails as much as 300 meters in diameter, while still needing to keep our sail material astonishingly thin and capable of surviving the perihelion temperatures. Operating at deep perihelia with metamaterials is a subject still very low on the TRL level, meaning technical readiness to produce and fly such a sail is nowhere near where it needs to be if we are to launch in the 2035-2040 window hoped for by mission planners. If we can launch multiple sails, we can consider self-assembly of the larger payload in transit, also at a very low TRL
Importantly, this maturity gap is not a physics limit: it is a program-and-demonstration limit. A focused late2020s/early-2030s development that couples (i) large-area deployment validation, (ii) deep-perihelion optical-property stability tests, and (iii) integrated areal-density demonstrations at the 104–105 m2 scale could credibly raise the SGL-class sail system TRL into the mission-start window, particularly for the 25–40 yr-class access regime.
Image: Sailcraft example trajectory toward the Solar Gravity Lens. Taken from an earlier report by Turyshev et al.
Nuclear electric propulsion (NEP) offers certain advantages over solar sails, including the fission reactor that powers its thrusters, for as mentioned, solar power at these distances is not practical. Turyshev’s calculations make the needed comparison, yielding a mission that can reach 650 AU in 27 years, putting it in range of what the sail strategy can deliver. Using propellant remaining in the craft upon arrival at the SGL, our spacecraft can now manage station-keeping and trajectory changes necessary to collect the needed pixels of our exoplanet image. In terms of operations, then, as well as payload capability, NEP stands out. Note that here again we have thermal issues, for the NEP-powered craft will need their own close perihelion pass to boost velocity. Turyshev points out that NEP will also demand large, deployable radiators to allow the escape of waste heat.
Nuclear thermal propulsion (NTP) now comes into the discussion, as the author considers potential hybrid missions. In NTP, liquid hydrogen is heated by the reactor core to produce thrust through the exhaust nozzle. Capable of high specific impulse, this method is treated here as “a high-thrust injection stage,” one that could be used during an Oberth maneuver to increase the velocity of an NEP-equipped spacecraft. The nuclear issues persist: We need safety analyses and ground testing facilities for the reactor, radiological handling protocols, and additional flight approval processes.
The three propulsion options play against each other in interesting ways. Sails avoid the problem of flight approval for nuclear materials as well as necessary infrastructure for ground testing. But materials and deployment issues still exist for these ultra-thin sails. An NEP engine that offers wider use beyond the SGL mission could lower incremental costs. And what if we tinker with mission duration? The fact remains that regardless of the choice of propulsion, we still have to operate in an environment that requires radioisotope or fission power, with all the implications for payload overhead that entails.
Programmatically, a credible 2035–2040 start requires aligning architecture choice with what can be demonstrated by the early 2030s. If minimum TOF [time of flight] is the primary requirement, solar sailing (with an explicit deep-perihelion materials and deployment qualification program) remains the most schedule-aligned approach. If delivered capability and operational robustness at the SGL dominate, NEP is uniquely attractive, but a 2035–2040 launch that depends on NEP for transportation must be preceded by an integrated stage demonstration that retires system-level coupling risks (thermal, EMI/EMC [Electromagnetic Interference / Electromagnetic Compatibility], plume, autonomy, and nuclear approval). In either case, SGL transportation should be treated as flagship-class in development complexity because the critical path runs through integrated demonstrations rather than through single-component maturity.
This is how missions get designed, and you can see how involved the process becomes long before actual hardware is even built. My belief is that the question of the generation clock is fading, for in dealing with issues like the SGL, we’re forced to contemplate scenarios in which those who plan the mission may not see its completion (although I hope Slava Turyshev is very much an exception!) In sending missions beyond the Solar System, we create gifts of data to future generations, who may well use what the SGL finds to plan missions much further afield, perhaps all the way to Proxima Centauri b.
The paper is Turyshev, “Propulsion Trades for a 2035-2040 Solar Gravitational Lens Mission,” currently available as a preprint. For more on acquisition of the lensed image, see Geoffrey Landis’ extremely useful slide presentation.
A Relativistic Explanation for the Dearth of Circumbinary Planets
Planets orbiting two stars have been found, but not all that many of them. We’re talking here about a planet that orbits both stars of a close binary system, and thus far, although we’ve confirmed over 6,000 exoplanets, we’ve only found 14 of them in this configuration. Circumbinary planets are odd enough to make us question what it is we don’t know about their formation and evolution that accounts for this. Now a paper from researchers at UC-Berkeley and the American University of Beirut probes a mechanism Einstein would love.
At play here are relativistic effects, having to do with the fact that, as Einstein explained, intense gravitational fields have detectable effects upon the stars’ orbits. This is hardly news, as it was the precession of Mercury in the sky that General Relativity first predicted. The planet’s orbit could be seen to precess (shift) by 43 arcseconds per century more than was expected by Newtonian mechanics. Einstein showed in 1915 that spacetime curvature could account for this, and calculated the exact 43 arcsecond shift astronomers observed.
What we see in close binary systems is that if we diagram the elliptical orbit usually found in such systems, the line connecting the closest approach (periastron) and farthest point in the orbit (apoapsis) gradually rotates. The term for this is apsidal precession. This precession – rotation of the orbital axis – is coupled with tidal interactions between the two stars, which make their own contribution to the effect. Close binary orbits, then, should be seen as shifting over time, partly as a consequence of General Relativity.
The researchers calculate that as the precession rate of the stars increases, that of a planet orbiting both stars slows. The planet’s perturbation can be accounted for by Newtonian mechanics, and its lessening precession is the result of tidal effects gradually shrinking the orbit of the two binary stars. But note this: When the two precession rates match, or come into resonance, the planet experiences serious consequences. Mohammad Farhat, (UC Berkeley) and first author of the paper, phrases the matter this way:
“Two things can happen: Either the planet gets very, very close to the binary, suffering tidal disruption or being engulfed by one of the stars, or its orbit gets significantly perturbed by the binary to be eventually ejected from the system. In both cases, you get rid of the planet.”
Image: An artist’s depiction of a planet orbiting a binary star. Here, the stars have radically different masses and as they orbit one another, they tug the planet in a way that makes the planet’s orbit slowly rotate or precess. Based on dynamic modeling, general relativistic effects make the orbit of the binary also precess. Over time, the precession rates change and, if they sync, the planet’s orbit becomes wildly eccentric. This causes the planet to either get expelled from the system or engulfed by one of the stars. Credit: NASA GSFC.
Does this mean that circumbinary planets are rare, or does it imply that most of them are probably in outer orbits and hard to find by our current methods? Ejection from the system seems the most likely outcome, but who knows? The researchers make three points about this. Quoting the paper:
(i) Systems that result in tight binaries (period ≤ 7.45 days, that of Kepler-47) via orbital decay are more likely than not deprived of a companion planet: the resonance-driven growth of the planet’s eccentricity typically drives it into the throes of its host’s driven instabilities, leading to ejection or engulfment by that host.
(ii) Planetary survivors of the sweeping resonance mostly reside far from their host and are therefore less likely to have their transits detected. Should eccentric survivors nevertheless be detected, they are expected to bear the signature of resonant capture into apse alignment with the binary.
(iii) The process appears robust to the modeling of the initial binary separation, with three out of four planets around tight binaries experiencing disruption…
What we wind up with here is that circumbinary planets are hard to find, but the greatest scarcity is going to be circumbinaries around binary systems whose orbital period is seven days or less. The researchers note that 12 of the 14 known circumbinary planets are close to but not within what they describe as the ‘instability zone,’ where these effects would be the strongest. Indeed, the combination of general relativistic effects and tidal interactions is calculated here to disrupt planets around tight binaries about 80 percent of the time. Most of the planets thus disrupted would most likely be destroyed in the process.
The paper is Farhat & Touma, “Capture into Apsidal Resonance and the Decimation of Planets around Inspiraling Binaries,” Astrophysical Journal Letters Vol. 995, No. 1 (8 December 2025), L23. Full text.
A New Tool for Exoplanet Detection and Characterization
It’s been apparent for a long time that far more astronomical data exist than anyone has had time to examine thoroughly. That’s a reassuring thought, given the uses to which we can put these resources. Ponder such programs as Digital Access to a Sky Century at Harvard (DASCH), which draws on a trove of over half a million glass photographic plates dating back to 1885. The First and Second Palomar Sky Surveys (POSS-1 and POSS-2) go back to 1949 and are now part of the Digitized Sky Survey, which has digitized the original photographic plates. The Zwicky Transient Facility, incidentally, uses the same 48-inch Samuel Oschin Schmidt Telescope at Palomar that produced the original DSS data.
There is, in short, plenty of archival material to work with for whatever purposes astronomers want to pursue. You may remember our lengthy discussion of the unusual star KIC 8462852 (Boyajian’s Star), in which data from DASCH were used to explore the dimming of the star over time, the source of considerable controversy (see, for example, Bradley Schaefer: Further Thoughts on the Dimming of KIC 8462852 and the numerous posts surrounding the KIC 8462852 phenomenon in these pages). Archival data give us a window by which we can explore a celestial observation through time, or even look for evidence of technosignatures close to home (see ‘Lurker’ Probes & Disappearing Stars).
But now we have an entirely new class of archival data to mine and apply to the study of exoplanets. A just published paper discusses how previously undetectable data about stars and exoplanets can be found within the archives of radio astronomy surveys. The analysis method has the name Multiplexed Interferometric Radio Spectroscopy (RIMS), and it’s intriguing to learn that it may be able to detect an exoplanet’s interactions with its star, and even to run its analyses on large numbers of stars within the radio telescope’s field of view.
We are in the early stages of this work, with the first detections now needing to be further analyzed and subsequent observations made to confirm the method, so I don’t want to minimize the need for continuing study. But if things pan out, we may have added a new method to our toolkit for exoplanet detection.
The signature finding here is that the huge volumes of data accumulated by radio telescopes worldwide, so vital in the study of cosmology through the analysis of galaxies and black holes, can also track variable activity of numerous stars that are within the field of view of each of these observations. What the authors are unveiling here is the ability to perform a simultaneous survey across hundreds or potentially thousands of stars. Cyril Tasse, lead author of the paper in Nature Astronomy, is an astronomer at the Paris Observatory. Tasse explains the range that RIMS can deploy:
“RIMS exploits every second of observation, in hundreds of directions across the sky. What we used to do source by source, we can now do simultaneously. Without this method, it would have taken nearly 180 years of targeted observations to reach the same detection level.”
The researchers have examined 1.4 years of data collected at the European LOFAR (Low Frequency Array) radio telescope at 150 MHz. Here low frequency wavelengths from 10 to 240 MHz are probed by a huge array of small, fixed antennas, with locations spread across Europe, their data digitized and combined using a supercomputer at the University of Groningen in the Netherlands. Out of this data windfall the RIMS team has been able to generate some 200,000 spectra from stars, some of them hosting exoplanets. While a stellar explanation is possible for star-planet interactions, this form of analysis, say the authors, “demonstrate[s] the potential of the method for studying stellar and star–planet interactions with the Square Kilometre Array.” LOFAR can be considered a precursor to the low-frequency component of the SKA.
Here we drill down to the planetary system level, for among the violent stellar events that RIMS can track (think coronal mass ejections, for example), the researchers have traced signals that produce what we would expect to find with magnetic interactions between planet and star. Closer to home, we’ve investigated the auroral activity on Jupiter, but now we may be tracing similar phenomena on planets we have yet to detect through any other means.
Image: Artistic illustration of the magnetic interaction between a red dwarf star such as GJ 687, and its exoplanet. Credit: Danielle Futselaar/Artsource.nl.
Let’s focus for a moment on the importance of magnetic fields when it comes to making sense of stellar systems other than our own. The interior composition of planets – their internal dynamo – can be explored with a proper understanding of their magnetosphere, which also unlocks information about the parent star. That sounds highly theoretical, but on the practical plane it points toward a signal we want to acquire from an exoplanetary system in order to understand the environments present on orbiting worlds. And don’t forget how critical a magnetic field is in terms of habitability, for fragile atmospheres must be shielded from stellar winds so as to be preserved.
At the core of the new detection method is cyclotron maser instability(CMI), which is the basic process that produces the intense radio emissions we see from planets like Jupiter. CMI is an instability in a plasma, where electrons moving in a magnetic field produce coherent electromagnetic radiation. Here is a link to Juno observations of these phenomena around Jupiter.
Detecting such emissions, RIMS can point to the presence of a planet in a stellar system. Working with radio observations, we can move beyond modeling to sample actual field strengths, which is why radio emissions (not SETI!) from exoplanets have been sought for decades now. Finding a way to produce interferometric data sufficient to paint a star-planet signature is thus a priority.
Exoplanetary aurorae would indicate the existence of magnetospheres, and that’s no small result. And we may be making such a detection around a star some 14.8 light years away, says co-author Jake Turner (Cornell University):
“Our results indicate that some of the radio bursts, most notably from the exoplanetary system GJ 687, are consistent with a close-in planet disturbing the stellar magnetic field and driving intense radio emission. Specifically, our modeling shows that these radio bursts allow us to place limits on the magnetic field of the Neptune-sized planet GJ 687 b, offering a rare indirect way to study magnetic fields on worlds beyond our Solar System.”
There are also implications for the search for life elsewhere in the cosmos. Turner adds:
“Exoplanets with and without a magnetic field form, behave and evolve very differently. Therefore, there is great need to understand whether planets possess such fields. Most importantly, magnetic fields may also be important for sustaining the habitability of exoplanets, such as is the case for Earth,”
Using low-frequency radio astronomy, then, we turn a telescope array into a magnetosphere detector. Researchers have also applied the MIMS technique to the French low frequency array NenuFAR, located at the Nançay Radio Observatory south of Paris, detecting a burst from the exoplanetary system HD 189733 that was described recently in Astronomy & Astrophysics. As with another possible burst from Tau Boötes, the team is in the midst of making follow-up observations to confirm that both signals came from a star-planet interaction. If the method is proven successful, such interactions point to a new astronomical tool.
The paper is Tasse et al., “The detection of circularly polarized radio bursts from stellar and exoplanetary systems,” Nature Astronomy 27 January 2026 (abstract). The earlier paper is Zhang et al., “A circularly polarized low-frequency radio burst from the exoplanetary system HD 189733,” Astronomy & Astrophysics Vol. 700, A140 (August 2025). Full text.
Holography: Shaping a Diffractive Sail
One result of the Breakthrough Starshot effort has been an intense examination of sail stability under a laser beam. The issue is critical, for a small sail under a powerful beam for only a few minutes must not only survive the acceleration but follow a precise trajectory. As Greg Matloff explains in the essay below, holography used in conjunction with a diffractive sail (one that diffracts light waves through optical structures like microscopic gratings or metamaterials) can allow a flat sail to operate like a curved or even round one. I’ll have more on this in terms of the numerous sail papers that Starshot has spawned soon. For today, Greg explains how what had begun as an attempt to harness holography for messaging on a deep space probe can also become a key to flight operations. The Alpha Cubesat now in orbit is an early test of these concepts. The author of The Starflight Handbook among many other books (volumes whose pages have often been graced by the artwork of the gifted C Bangs), Greg has been inspiring this writer since 1989.
by Greg Matloff
The study of diffractive photon sails likely begins in 1999 during the first year of my tenure as a NASA Summer Faculty Fellow. I was attending an IAA symposium in Aosta, Italy where my wife C Bangs curated a concurrent art show. The title of the show , which included work by about thirty artists, was “Messages from Earth”. At the show’s opening, C was approached by visionary physicist Robert Forward who informed her that the best technology to affix a message plaque to an interstellar photon sail was holography. A few weeks later, back in Huntsville AL, Bob suggested to NASA manager Les Johnson that he fund her to create a prototype holographic interstellar message plaque.
It is likely that Bob encouraged this art project as an engineering demonstration. He was aware that photon sails do not last long in Low Earth Orbit because the optimum sail aspect angle to increase orbital energy is also the worst angle to increase atmospheric drag. He had experimented with the concept of a two-sail photon sail and correctly assumed that from a dynamic point of view such a sail would fail. A thin-film hologram of an appropriate optical device could redirect solar radiation pressure accurately without increasing drag.
Our efforts resulted in the creation of a prototype holographic interstellar message plaque that is currently at NASA Marshall Space Flight Center. It was displayed to NASA staff during the summer of 2001 and has been described in a NASA report and elsewhere [1].
I thought little about holography until 2016, when I was asked by Harvard’s Avi Loeb to participate in Breakthrough Starshot as a member of the Scientific Advisory Committee. This technology development project examined the possibility of inserting nano-spacecraft into the beam of a high energy laser array located on a terrestrial mountain top. The highly reflective photon sail affixed to the tiny payload could in theory be accelerated to 20% of the speed of light.
One of the major issues was sail stability during the 5-6 minutes in a laser beam moving with Earth’s rotation. Work by Greg and Jim Benford, Avi Loeb and Zac Manchester (Carnegie Mellon University) indicated that a curved sail was necessary. to compensate for beam motion. But a curved thin sail would collapse immediately during the enormous acceleration load.
Some researchers realized that a diffractive sail that could simulate a curved surface might be necessary. Grover Swartzlander of Rochester Institute of Technology published on the topic [2].
Martina Mongrovius, then Creative Director of the NYC HoloCenter, suggested to C that one approach to incorporating an image of an appropriate diffractive optical device in the physically flat sail was holography; this was later confirmed by Swartzlander. Avi Loeb arranged for C to attend the 2017 Breakthrough meeting and demonstrate our version of the prototype holographic message plaque.
A Breakthrough Advisor present at the demonstration was Cornell professor and former NASA chief technologist Mason Peck. Mason invited C to create, with Martina’s aid, five holograms to be affixed to Cornell’s Alpha CubeSat, a student-coordinated project to serve as a test bed for several Starshot technologies.
Image: Fish Hologram (Sculpture by C Bangs, exposure by Martina Mrongovius). A holographic plaque could carry an interstellar message. But could holography also be used to simulate the optimal sail surface on a flat sail?
During the next eight years, about 100 Cornell aerospace engineering students participated in the project. Doctoral student Joshua Umansky-Castro, who has now earned his Ph.D. was the major coordinator.
In 2023, there was an exhibition aboard the NYC museum ship Intrepid (a World War II era aircraft carrier) presenting the scientific and artistic work of the Alpha CubeSat team. Alpha was launched in September of 2025 as part of a ferry mission to the ISS. The cubesat was deployed in Dec. 2025.
All goals of the effort have been successfully achieved. The tiny chipsats continue to communicate with Earth. The demonstration sail deployed as planned from the CubeSat. A post-deployment glint photographed from the ISS indicates that the holograms perform in space as expected, increasing the Technological Readiness of in-space holograms and diffraction sailing.
In May 2026 a workshop on Lagrange Sunshades to alleviate global warning is scheduled to take place in Nottingham. The best sunshade concepts suggested to date are reflective sails. Two issues with reflective sail sunshades are apparent. One is the meta-stability of L1, which requires active control to maintain the sunshade on station. A related issue is that the solar radiation momentum flux moves the effective Lagrange point farther from the Earth, requiring a larger sunshade. At the Nottingham Workshop. C and I will collaborate with Grover Swartzlander to demonstrate how a holographic/diffractive sunshade surface alleviates these issues.
References
1.G. L. Matloff, G. Vulpetti, C. Bangs and R. Haggerty, “The Interstellar Probe (ISP): Pre-Perihelion Trajectories and Application of Holography”, NASA/CR-2002-211730, NASA Marshal Spaceflight Center, Huntsville, AL (June, 2002). Also see G. L. Matloff, Deep-Space Probes: To the Outer Solar System and Beyond, 2nd. ed., Springer/Praxis, Chichester, UK (2005).
2.G. A. Swartzlander, Jr., “Radiation Pressure on a Diffractive Sailcraft”, arXiv: 1703.02940.
Shelter from the Storm
The approaching storm will almost certainly cause power outages that will make it impossible to post here. If this occurs, you can be sure that I’ll get any incoming messages posted as soon as I can get back online. Please continue to post comments as usual and let’s cross our fingers that the storm is less dangerous than it appears.
Cellular Cosmic Isolation: When the Universe Seeds Life but Civilizations Stay Silent
So many answers to the Fermi question have been offered that we have a veritable bestiary of solutions, each trying to explain why we have yet to encounter extraterrestrials. I like Leo Szilard’s answer the best: “They are among us, and we call them Hungarians.” That one has a pedigree that I’ll explore in a future post (and remember that Szilard was himself Hungarian). But given our paucity of data, what can we make of Fermi’s question in the light of the latest exoplanet findings? Eduardo Carmona today explores with admirable clarity a low-drama but plausible scenario. Eduardo teaches film and digital media at Loyola Marymount University and California State University Dominguez Hills. His work explores the intersection of scientific concepts and cinematic storytelling. This essay is adapted from a longer treatment that will form the conceptual basis for a science fiction film currently in development. Contact Information: Email: eduardo.carmona@lmu.edu
by Eduardo Carmona MFA
In September 2023, NASA’s OSIRIS-REx spacecraft delivered a precious cargo from asteroid Bennu: pristine samples containing ribose, glucose, nucleobases, and amino acids—the molecular Lego blocks of life itself. Just months later, in early 2024, the Breakthrough Listen initiative reported null results from their most comprehensive search yet: 97 nearby galaxies across 1-11 GHz, with no compelling technosignatures detected.
We live in a cosmos that generously distributes life’s ingredients while maintaining an eerie radio silence. This is the modern Fermi Paradox in stark relief: building blocks everywhere, conversations nowhere.
What if both observations are telling us the same story—just from different chapters?
The Seeding Paradox
The discovery of complex organic molecules on Bennu—a pristine carbonaceous asteroid that has barely changed in 4.5 billion years—confirms what astrobiologists have long suspected: the universe is in the business of making life’s components. Ribose, the sugar backbone of RNA. Nucleobases that encode genetic information. Amino acids that fold into proteins.
These aren’t laboratory curiosities. They’re delivered at scale across the cosmos, frozen in time capsules of rock and ice, raining down on every rocky world in every stellar system. The implications are profound: prebiotic chemistry isn’t a lottery. It’s standard operating procedure for the universe.
This abundance makes the silence more puzzling. If life’s ingredients are everywhere, why isn’t life—or at least communicative life—equally ubiquitous? The Drake Equation suggests we should be drowning in signals. Yet decade after decade of increasingly sophisticated SETI searches return the same answer: nothing.
The traditional responses—they’re too far away, they use technology we can’t detect, they’re deliberately hiding—feel increasingly like special pleading. What if the answer is simpler, more systemic, and reconcilable with both observations?
Cellular Cosmic Isolation: A Synthesis
I propose what I call Cellular Cosmic Isolation (CCI)—not a single explanation but a framework that synthesizes multiple constraints into a coherent picture. Think of it as a series of filters, each one narrowing the funnel from chemical abundance to electromagnetic chatter.
The framework rests on four interlocking observations:
1. Prebiotic abundance: Chemistry is generous. Small bodies deliver life’s building blocks widely and consistently. Biospheres may be common.
2. Geological bottlenecks: Complex, communicative life requires rare conditions—specifically, worlds with coexisting continents and oceans, sustained by long-duration plate tectonics (≥500 million years). Earth’s particular geological engine may be uncommon.
3. Fleeting windows: Technological civilizations may have extraordinarily brief outward-detectable phases—measured in decades, not millennia—before transitioning to post-biological forms, self-destruction, or simply turning their attention inward.
4. Communication constraints: Physical limits (finite speed of light, signal dispersion, beaming requirements) plus coordination problems suppress even the detection of civilizations that do exist.
The result? A universe where the chemistry of life is ubiquitous, simple biospheres may be common, but detectable technospheres remain vanishingly rare and non-overlapping in spacetime. We’re not alone because life is impossible. We’re alone because the path from ribose to radio telescopes has far more gates than we imagined.
The Geological Filter: Earth’s Unlikely Engine
This is perhaps CCI’s most counterintuitive claim, yet it’s grounded in recent research. In a 2024 paper in Scientific Reports, planetary scientists Robert Stern and Taras Gerya argue that Earth’s specific combination—plate tectonics that has operated for billions of years, creating and recycling continents alongside persistent oceans—may be geologically unusual.
Why does this matter for intelligence? Because continents enable:
• Terrestrial ecosystems with high energy density and environmental diversity
• Land-ocean boundaries that create evolutionary pressure for complex sensing and locomotion
• Fire (impossible underwater), which enables metallurgy and advanced tool use
• Seasonal and altitudinal variation that rewards cognitive flexibility
Venus has no plate tectonics. Mars lost its early tectonics. Europa and Enceladus have subsurface oceans but no continents. Earth’s geological engine—stable enough to persist for billions of years, dynamic enough to continuously create new land and recycle old—may be a rare configuration.
Mathematically, this adds two probability terms to the Drake Equation: foc (the fraction of habitable worlds with coexisting oceans and continents) and fpt (the fraction with sustained plate tectonics). If each is, say, 0.1-0.2, their joint probability becomes 0.01-0.04—already a significant filter.
The Temporal Filter: Civilization’s Brief Bloom
But the most devastating filter may be temporal. Traditional SETI assumes civilizations remain detectably technological for thousands or millions of years. CCI suggests the opposite: the phase during which a civilization broadcasts electromagnetic signals into space may be extraordinarily brief—perhaps only decades to centuries.
Consider the human trajectory. We’ve been radio-loud for roughly a century. But already:
• We’re transitioning from broadcast to narrowcast (cable, fiber, satellites)
• Our strongest signals are becoming more controlled and directional
• We’re developing AI systems that may fundamentally transform human civilization within this century
What comes after? Post-biological intelligence operating at computational speeds? A civilization that turns inward, exploring virtual realities? Self-annihilation? Deliberate silence to avoid dangerous contact?
We don’t know. But if the detectable technological phase (call it Lext) averages 50-200 years rather than 10,000-1,000,000 years, the probability of temporal overlap collapses. In a galaxy 13 billion years old, two civilizations with century-long detection windows need to be synchronized to within a cosmic eyeblink.
This isn’t speculation—it’s extrapolation from our own accelerating technological trajectory. And acceleration may be a universal property of technological intelligence.
The Mathematics of Solitude
The traditional Drake Equation multiplies probabilities: star formation rate × fraction with planets × habitable planets per system × fraction developing life × fraction developing intelligence × fraction developing communication × longevity of civilization.
CCI expands this with additional constraints:
Ndetectable = R* × Tgal × [biological/technological terms] × [foc × fpt] × [Lext / Tgal] × C(I)
Where C(I) captures propagation physics—distance, dispersion, scattering, beaming geometry. Each term is a probability distribution, not a point estimate.
In 2018, Oxford researchers Anders Sandberg, Stuart Armstrong, and Milan Ćirković performed a rigorous Bayesian analysis of Drake’s Equation using probability distributions for each parameter. Their conclusion? When uncertainties are properly handled, the probability that we are alone in the observable universe is substantial—not because life is impossible, but because the error bars are enormous.
CCI takes this Bayesian framework and adds the geological and temporal constraints. The result: a posterior probability distribution that is entirely consistent with both abundant prebiotic chemistry and persistent SETI nulls. No paradox required.
What We Should See (And Why We Don’t)
CCI makes testable predictions. If the framework is correct:
1. Biosignatures before technosignatures
Upcoming missions like the Habitable Worlds Observatory should detect atmospheric biosignatures (oxygen-methane disequilibria, possible vegetation edges) before detecting techno signatures. Simple biospheres should be discoverable; technospheres should remain elusive.
2. Continued SETI nulls
Radio and optical SETI campaigns will continue to find nothing—not because we’re searching wrong, but because the detectable population is genuinely sparse and temporally fleeting.
3. Technosignature detection requires extreme investment
Detection of artificial spectral edges (like photovoltaic arrays reflecting at silicon’s UV-visible cutoff) or Dyson-sphere waste heat requires hundreds of hours of observation time even for nearby stars. Their absence at practical survey depths is predicted, not puzzling.
Importantly, CCI is falsifiable. A single unambiguous, repeatable interstellar signal would invalidate the short-Lext assumption. Multiple detections of artificial spectral features would refute the geological filter. The framework lives or dies by observation.
The Cosmos as Organism
There’s an almost biological elegance to this picture. The universe manufactures prebiotic molecules in stellar nurseries and delivers them via comets and asteroids—a kind of cosmic panspermia that doesn’t require directed intelligence, just chemistry and gravity. Call it the seeding phase.
Some of those seeds land on worlds with the right geological configuration—the awakening phase—where continents and oceans coexist long enough for complex cognition to emerge. This is rarer.
A tiny fraction of those awakenings reaches technological sophistication—the communicative phase—but this phase is fleeting, measured in decades to centuries before transformation or silence. This is rarest.
And even then, physical constraints—distance, timing, beaming, the sheer improbability of coordination—suppress detection. The isolation phase.
The cosmos isn’t hostile to intelligence. It’s just structured in a way that makes electromagnetic conversation between civilizations vanishingly unlikely—not impossible, just so improbable that null results after decades of searching are exactly what we’d expect.
Each civilization, then, is like a cell in a vast organism: seeded with the same chemical building blocks, developing according to local conditions, briefly active, then transforming or falling silent before contact with other cells occurs. Cellular Cosmic Isolation.
What This Means for Us
If CCI is correct, we should recalibrate our expectations without abandoning hope. SETI is not futile—it’s hunting for an extraordinarily rare phenomenon. Every null result tightens our probabilistic constraints and guides future searches. But we should also prepare for the possibility that we are, if not alone, then at least effectively alone during our detectable window.
This shifts the weight of responsibility. If technological civilizations are rare and fleeting, then ours carries unique value—not as a recipient of cosmic wisdom from older civilizations, but as a brief, precious experiment in consciousness. The burden falls on us to use our detectable phase wisely: to either extend it, transform it into something sustainable, or at least ensure we don’t waste it.
The universe seeds life generously. It’s indifferent to whether those seeds grow into forests or fade into silence. CCI suggests that the path from chemistry to conversation is longer, stranger, and more filtered than we imagined.
But the building blocks are everywhere. The recipe is universal. And somewhere, in the vast probabilistic landscape of possibility, other cells are awakening. We just may never hear them call out before they, like us, transform into something we wouldn’t recognize as a civilization at all.
That is not a paradox. That is simply the way the cosmos works.
Further Reading
Prebiotic Chemistry:
Furukawa, Y., et al. (2025). “Detection of sugars and nucleobases in asteroid Ryugu samples.” Nature Geoscience. NASA’s OSIRIS-REx mission (2023) also reported similar findings from Bennu.
Bayesian Drake Analysis:
Sandberg, A., Drexler, E., & Ord, T. (2018). “Dissolving the Fermi Paradox.” arXiv:1806.02404. Oxford Future of Humanity Institute.
Geological Filters:
Stern, R., & Gerya, T. (2024). “Plate tectonics and the evolution of continental crust: A rare Earth perspective.” Scientific Reports, 14.
SETI Null Results:
Choza, C., et al. (2024). “A 1-11 GHz Search for Radio Techno signatures from the Galactic Center.” Astronomical Journal. Breakthrough Listen campaign results.
Barrett, J., et al. (2025). “An Exoplanet Transit Search for Radio Techno signatures.” Publications of the Astronomical Society of Australia.
Technosignature Detection:
Lingam, M., & Loeb, A. (2017). “Natural and Artificial Spectral Edges in Exoplanets.” Monthly Notices of the Royal Astronomical Society Letters, 470(1), L82-L86.
Kopparapu, R., et al. (2024). “Detectability of Solar Panels as a Techno signature.” Astrophysical Journal.
Wright, J. et al (2022). “The Case for Techno signatures: Why They May Be Abundant, Long-lived, and Unambiguous.” The Astrophysical Journal Letters 927(2), L30.
Technology Acceleration:
Garrett, M. (2025). “The longevity of radio-emitting civilizations and implications for SETI.” Journal of the British Interplanetary Society (forthcoming). See also earlier work on technological singularities and post-biological transitions.
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